The present invention relates to a wire catalyst (and shaped wire catalyst) for hydrogenation/dehydrogenation reactions which shows good catalytic activity in a hydrogenation reaction of an aromatic compound and/or a dehydrogenation reaction of a hydrogen derivative of an aromatic compound, and also relates to a method for manufacturing the wire catalyst (and shaped wire catalyst).
In recent years, global warming is seen as a problem, and a fuel cell system attracts attention as a clean energy as an alternative to fossil fuels. Especially, hydrogen attracts attention as a fuel of such fuel cell system.
In the fuel cell system using hydrogen as fuel, discharged during generating electric power is only water, therefore, such system attracts attention as an energy source whose environmental load is smallest, in other words, which is most environmentally friendly and clean.
On the other hand, in the case of engines of gasoline automobiles, diesel generators for ships/locomotives, etc., by employing “hydrogen-oil co-combustion technique” in which hydrogen is added to the fuel oil, it is possible to improve fuel consumption and reduce the generation of substances becoming environment loads, e.g. CO2, NOx, CO and the like.
Meanwhile, hydrogen is gaseous body at ordinary temperatures and a combustible and explosive substance. Therefore, hydrogen has problems with its storage and transportation.
Currently, therefore, studies are being made on a hydrogen storage-supply system capable of storing hydrogen safely and capable of supplying hydrogen quickly responding to the demand.
At present, the following methods have been proposed as methods for supplying hydrogen:
A) a method in which hydrogen is stored in a cylinder or tank and delivered to end users,
B) a method in which hydrogen is prepared from city gas or propane gas established as infrastructures by means of a steam reforming technique or the like,
C) a method in which hydrogen is made by electrolysis of H2O utilizing surplus nighttime electric power,
D) a method in which hydrogen is made by electrolysis of H2O utilizing electric power produced by wind power, solar energy and the like,
E) a method in which hydrogen is made by utilizing photosynthesis bacteria, anerobic hydrogen bacteria and the like.
Among these methods, the method (A) is readily feasible as a hydrogen supply system, but it is supposed that this system is gradually restricted in view of safety issues because hydrogen is combustible gas.
In the case of the method (B), on the other hand, it is possible to utilize the existing gas pipings. From this viewpoint, this method is feasible, but the reforming devices are usually not good at the productivity rate of hydrogen and the hydrogen supplying response.
Further, there is a problem such that purification/elimination of poisonous constituents such as CO produced as by-products increases the processing cost.
In the case of the methods (C)-(E), a time-lag is liable to occur between demand of hydrogen and the supply, therefore, there is a problem such that the supply of hydrogen is hard to follow the load changes caused by electrical demand changes.
In order to bring about the realization of the methods B-E which have potential of practical applications, studies are made on efficient hydrogen storage/supplying system which can store the produced hydrogen and can supply the stored hydrogen to a fuel-cell-system, internal-combustion engine or the like in good response to the need.
To give actual examples of such system, in Japanese patent application publication Nos. JP-7-192746 and JP-5-270801,
a system utilizing a hydrogen storage alloy, and
a system utilizing a carbon material such as carbon nanotube, carbon nanofiber or the like have been disclosed.
Further, in Japanese patent application publication No. JP-4-354544, there has been disclosed a catalyst structure which is supported on the surface of a metal which is material shaped in the form of a wire, filament, fine tube, mesh or fabric, and
this shaped metal material is provided with a surface layer which is made of aluminum oxide or comprises aluminum oxide as its major component. And it is also disclosed that platinum, palladium and ruthenium can be used as the catalyst.
By employing a hydrogen storage alloy, it is possible to construct such a system that the storage and extraction of hydrogen can be easily controlled by the temperature.
But, the amount of storage of hydrogen per unit weight of the alloy is small. For example, in the case of a typical hydrogen storage alloy LaNi, the amount of hydrogen storage is about 3 wt % at best.
Further, the rate of storage or extraction of hydrogen is low, therefore, there is a problem with the response. Furthermore, due to the hydrogen storage alloy itself, the system has disadvantages such that the weight and cost of the system are inevitably increased.
In the case of the system utilizing the carbon material, on the other hand, materials having high hydrogen storage amount are now being developed, but the hydrogen storage amount is not yet sufficient.
In addition, these materials are difficult to synthesize industrially on a large scale, therefore, due to the cost and quality of the obtained carbon materials, this system has not yet reached to a practical level.
In the above-mentioned Japanese patent application publication No. JP-4-354544, the disclosed object is merely to increase the catalytic reaction (or the amount of the catalyst per unit volume). There is no disclosure about how to improve the response of the catalytic reaction.